![]() There are many different factors that can effect pull out strength, but the main factors are the diameter of the fastener, the diameter of the threads, and the density of the substrate. Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.Pull out strength is the amount of pounds it takes to pull a fastener out of a given substrate using upward force. What are the hazards to avoid when going into an attic?.Why does my homeowner's insurance want a roof inspection?.How can I tell if the house needs a new roof?.Do stains on the ceiling mean the roof is leaking?.What does a home inspector look for when examining a roof?.What's the difference between an "architectural" and a regular shingle roof?.How much of a roof truss can I cut out to make a storage platform in the attic?.Do home inspectors go on the roof? Do they get in the attic?.What does "lack of tab adhesion" in an asphalt shingle roof mean?.What are those metal boxes on the roof?.Should I buy a house that needs a new roof?.What are the warning signs of a dangerous attic pull-down ladder?.Can metal roofing be used on a low slope/pitch roof?.What are the dark lines running parallel to shingles on my roof?.How many layers of roofing are allowed on a home?.How can I be sure my roofing contractor got a permit?.If my roof is not leaking, why does it need to be replaced?.What are the most common problems with wood roof trusses?.Why is a popped nail in a shingle roof a problem? How do I fix it?.Are roof trusses better than roof rafters (stick framing)?.Does a roof with multiple layers of shingles last longer?.What is the building code requirement for an attic access hatch, scuttle, or door?.Why is there no attic access hatch in the house?.Why is it a mistake to replace a roof and not replace its flashings?.What is the life expectancy of an asbestos cement shingle roof?.What are the common problems with attic insulation?.How can I tell if a roof has more than one layer of shingles?.Why is premature curl of roof shingles a problem?.How can I inspect my roof for hurricane damage?.Is an attic required to have a light by the building code?.Why does it cost so much more to replace a steep roof than a low slope roof?.What causes bubble-like blisters in a built-up and gravel roof?.What causes leaks at a fake roof dormer?.What causes shingles to buckle along a line on the roof?.What are the mistakes to avoid when doing attic improvements?.Why is granule loss a problem for an asphalt shingle roof?.Why is my roof sheathing sagging between the trusses?.To learn more about roofs and attics, see these other blog posts: To learn about two other visible roof problems and their cause, see our blog posts What causes roof shingles to curl up at corners? It may be necessary to wait for the materials to stabilize before determining whether any repairs or replacement is needed. And, of course, a roof leak can spread water under felts that sometimes migrates along the roof sheathing.Įliminating the moisture cures most buckling problems. A clothes dryer that terminates into the attic, or has vent through the roof that has become disconnected in the attic, is another source of water vapor and heat. If this requirement is ignored and the sheathing is butted tight, the wood has nowhere to go when the moisture makes it swell, except to curl up along the shared seam.Ī common cause of high humidity in an attic is lack of ventilation, which can be caused adding insulation that covers the soffit vents or lack of soffit vents and/or ridge vents altogether. An 1/8” gap is specified by manufacturers between sheets of plywood that are nailed side-by-side over a shared top chord of a roof truss or a rafter. However, a more pronounced buckling in a line running up the roof, like in the photo above, is caused by buckling of the edges of the plywood or OSB roof sheathing, due to water intrusion or extremely high humidity in the attic. But the moisture evaporates as the materials reach equilibrium with the the surrounding air, and the shingles settle back down flat. This then telegraphs to the shingles above. The wetness gets absorbed by the felt underlayment, causing the felt to wrinkle. Asphalt shingles sometimes buckle slightly, and in an irregular pattern, due to moisture in a the materials of a new roofing system.
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